There are many types of wetlands,  including such diverse areas such as tidal salt marshes, bottomland forests, conifer swamps, floodplain wet meadows, prairie potholes, bogs, vernal pools, and freshwater cattail marshes.  The common element in these habitats is the presence of water – which may be shallow standing water or saturated soil – possibly for only a portion of the growing season.   Only plants that can survive water-logged conditions will grow in wetlands, and the presence of these plants, along with wet soils, are used to help define wetland boundaries.

Various scientific and legal definitions of wetlands emphasize three characteristics:

• Wetlands either have shallow standing water, or soils that are saturated to the surface, at least for a period of time during the growing season;
  
  
• A wetland plant community includes vegetation that can grow in waterlogged conditions;
  
  
• Wetland soils are also specific to wetlands, showing signs of chemical changes that occur when saturated or flooded.

The difference among wetland types reflects the depth of water (or extent of soil saturation), and the sources of water.  Wetlands may be fed primarily by groundwater, by surface water, by precipitation, and by various combinations of the three sources.   Some types of wetlands are easier to restore or replace than others; for example, bogs – which are fed almost completely by precipitation, and which have peat soils – are almost impossible to re-create once they are destroyed because they take many decades to form naturally.   By contrast, cattail marshes are easier to restore provided that an appropriate supply of water is provided.

Scientist and various federal agencies have developed methods to identify and classify wetlands.   The U.S. Army Corps of Engineers has developed a wetland delineation manual, along with a number of regional supplements, to consistently identify wetland-upland boundaries.   For more information regarding wetland delineation methods, click here.